Haskell lazy I/O and closing files.

import Control.Monad
import Data.Digest.MD5 (hash)
import Data.Word
import List (sort)
import Prelude
import System.Directory
import System.FilePath
import Text.Printf (printf)
import qualified Data.ByteString.Lazy as BS

main :: IO ()

main = putStr . unlines =<< getList "."

getList :: FilePath -> IO [String]

getList p =
    let getFileLine path = liftM (\c -> (hex $ hash $ BS.unpack c) ++ " " ++ path) (BS.readFile path)
    in mapM getFileLine =<< getRecursiveContents p

hex :: [Word8] -> String

hex = concatMap (\x -> printf "%0.2x" (toInteger x))

getRecursiveContents :: FilePath -> IO [FilePath]

getRecursiveContents topdir = do
    names <- getDirectoryContents topdir

    let properNames = filter (`notElem` [".", ".."]) names

    paths <- concatForM properNames $ \name -> do
        let path = topdir </> name

        isDirectory <- doesDirectoryExist path
        if isDirectory
            then getRecursiveContents path
            else do
                isFile <- doesFileExist path
                if isFile
                    then return [path]
                    else return []

    return (sort paths)

concatForM :: (Monad m) => [a1] -> (a1 -> m [a]) -> m [a]

concatForM xs f = liftM concat (forM xs f)